Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-stateful-pce-auto-bandwidth-11: (with DISCUSS and COMMENT)
Dhruv Dhody <dhruv.ietf@gmail.com> Wed, 25 September 2019 08:27 UTC
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From: Dhruv Dhody <dhruv.ietf@gmail.com>
Date: Wed, 25 Sep 2019 13:56:46 +0530
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To: Benjamin Kaduk <kaduk@mit.edu>
Cc: The IESG <iesg@ietf.org>, draft-ietf-pce-stateful-pce-auto-bandwidth@ietf.org, Adrian Farrel <adrian@olddog.co.uk>, pce-chairs <pce-chairs@ietf.org>, pce@ietf.org
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Subject: Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-stateful-pce-auto-bandwidth-11: (with DISCUSS and COMMENT)
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Hi Ben, Thanks for the discussion. Snipping to open points.. > > > > > > As a general note, I'm not sure the phrase "calculated bandwidth to be > > > adjusted" is a great fit for how it's currently being used. > > > Specifically, the "calculation" in question seems to just be taking the > > > maximum of a sliding window of per-timeslice average bandwidth values, > > > and this seems like a sufficiently small amount of computation that I'd > > > be comfortable describing it as a "measurement", for "measured bandwidth > > > as input to path calculation". That is, this doesn't seem like it comes > > > close to the amount of computation involved in actually computing paths, > > > so I keep misreading what information is being sent where. > > > > > > > In an earlier version there was a feature where the PCC could report > > the measured value at each sample interval (it moved to another > > document). IMHO for the clarity in the WG, it is still better to > > differentiate between the raw measured value (telemetry) and the value > > that is currently reported which is marked as "calculated". > > Ah, in that context it makes more sense to do it this way. Perhaps an > informative reference to the other document/usage and note about the > terminology would help, though? > I have added - "Another approach would be to send the measured values itself to the PCE, which is considered out of scope for this document.". In terminology I highlighted 'measured' and 'calculated' in the existing terms. > > > Section 1 > > > > > > Over time, based on the varying traffic pattern, an LSP established > > > with a certain bandwidth may require to adjust the bandwidth reserved > > > in the network dynamically. The head-end Label Switch Router (LSR) > > > monitors the actual bandwidth demand of the established LSP and > > > periodically computes new bandwidth. The head-end LSR adjusts the > > > bandwidth reservation of the LSP based on the computed bandwidth > > > automatically. This feature is commonly referred to as Auto- > > > Bandwidth. The Auto-Bandwidth feature is described in detail in > > > Section 4 of this document. > > > > > > >From just this text, I can't tell if this is describing the mechanisms of > > > this document or an existing Auto-Bandwidth feature that is related to > > > the mechanisms of this document. > > > > > > > The auto-bandwidth feature without PCE exists, where the ingress does > > the measurement as well as path computation. This feature has been > > implemented long back but was not part of any standard because it was > > a local implementation at the ingress node and no protocol changes was > > required. With the PCE things changed and here we are... > > Ah, I see. Maybe "This feature, when available in the head-end LSR > implementation, is common referred to as [...]", then? > Updated. > > > Section 2.3 > > > > > > Are we assuming any relationship between the Up-Adjustment-Threshold and > > > the Overflow-Threshold? > > > > > > > Yes, as mentioned here while describing Overflow-Threshold - > > > > The LSP bandwidth is adjusted to the > > current bandwidth demand bypassing the Up-Adjustment-Interval if > > the overflow condition is met consecutively for the Overflow- > > Count. > > I was thinking more along the lines of if the Overflow-Threshold value was > going to be a larger number than the Up-Adjustment-Threshold. > Yes, I have added this in terminology section. Also added a note for operator to take care while setting this in section 6.1. I prefer to keep this generic as there are multiple combinations of formats to deal with. > > > > > traffic demand. If the percentage or absolute difference between > > > the current MaxAvgBw and the current bandwidth reservation of the > > > LSP is greater than or equal to the threshold value, the overflow > > > condition is set to be met. The LSP bandwidth is adjusted to the > > > > > > nit: I think s/set to be met/said to be met/ ? (this appears twice) > > > > > > > Ack > > > > > Minimum-Threshold: The increase or decrease of the LSP bandwidth > > > should be at least or above the minimum-threshold represented as > > > an absolute bandwidth value before the bandwidth adjustment for > > > the LSP is made. This threshold can be seen as a suppression > > > threshold that is used along with a percentage threshold to avoid > > > unnecessary auto-bandwidth adjustments and re-signaling of the LSP > > > at low bandwidth values. > > > > > > I can't tell from this text if this threshold is a (LSP) bandwidth > > > value/measurement or a bandwidth offset between configured and measured > > > values. (The subsequent protocol element definitions are more clear > > > that it's the latter.) > > > > > > > It is latter. Do you have a suggested change, I am not sure what change to make. > > How about: > > Minimum-Threshold: When percentage-based thresholds are in use, they > are accompanied by this minimum threshold, which is used to enforce > that the magnitude of deviation of calculated LSP bandwidth from the > reserved bandwidth exceeds a specific non-percentage-based criterion > before any adjustments are made. This serves to suppress unnecessary > auto-bandwidth adjustments and re-signaling of the LSP at low > bandwidth values. > > Thanks for the text. Updated with minor changes. > > > Section 4.2 > > > > > > When the Auto-Bandwidth feature is enabled, the measured traffic rate > > > is periodically sampled at each Sample-Interval (which can be > > > configured by an operator and the default value as 5 minutes) by the > > > PCC, when the PCC is the head-end node of the LSP. The traffic rate > > > > > > Do we cover what happens in the case when the PCC is not the head-end > > > node of the LSP? > > > > > > > No. > > Should we document that somewhere? > Added. Diff: https://tools.ietf.org/tools/rfcdiff/rfcdiff.pyht?url1=draft-ietf-pce-stateful-pce-auto-bandwidth-11&url2=https://raw.githubusercontent.com/dhruvdhody/ietf/master/draft-ietf-pce-stateful-pce-auto-bandwidth-12.txt Working Copy: https://raw.githubusercontent.com/dhruvdhody/ietf/master/draft-ietf-pce-stateful-pce-auto-bandwidth-12.txt Thanks! Dhruv
- [Pce] Benjamin Kaduk's Discuss on draft-ietf-pce-… Benjamin Kaduk via Datatracker
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Dhruv Dhody
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Dhruv Dhody
- Re: [Pce] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk